The telephone distribution system is changing and has changed from the old technique of one telephone per pair of wires in the distribution network to multiple digitally encoded phone connections per pair of wires, over at least part of the distribution network. An assembly (the Remote Unit) then decodes the digital data and distributes the information to multiple telephones. This change requires more power than that available or needed to power a simple telephone. The additional power has been traditionally supplied by a high direct current voltage delivered over the distribution system wire pairs (pair gain) to a remote unit using the same wire pair that carries the digitally encoded telephone traffic, or by local power utility company power. The preferred method for the telephone company is the line powered approach. This reduces the dependency of the telephone company on the local power grid. This allows the telephone company to maintain service even during power outages in the power utility network.
In many situations power is not only needed to run the telecommunications equipment but to provide power for other services such as monitoring, fault detection, cooling, life line services, and the like. With the increasing demand for data and limitations on power from central offices there is often insufficient power available to provide additional services by a single piece of equipment. In these types of situations any excess power available is often unused or unavailable
The increased complexity of remote equipment generally causes higher power requirements. With the increase in power at the remote unit thermal considerations become more important, in fact cooling air may be required. Additionally, the transmittable distance for the digital data, the power source voltage and wattage and the wiring loss, determine the signal source transmit distance. Both the power source and voltage are limited by constraints on the signal source. The minimum wire size and the length of the wire determine the wiring power loss. Since few of these constraints can be changed at the remote unit there is a need to minimize the power at the remote unit.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for a technique for providing cooling at remote units while minimizing power requirements.